Lake Baikal

Lake Baikal lies in south-eastern Siberia, in the Russian Federation, between the Republic of Buryatia and Irkutsk Oblast. The long lake occupies a steep-sided basin within the Baikal Rift Zone. At roughly 1.6 kilometres at its deepest point, it is the deepest lake in the world. Estimates of its age vary by source, but it is generally described as an ancient lake, roughly 20–25 million years old.

The Baikal basin is part of a continental rift system, where the Earth's crust is being extended and fractured. The U.S. Geological Survey describes the rift as a modern example that helps scientists study how continental margins form and, over geological time, can develop into ocean basins. Thick sediments accumulating in a large rift lake also preserve evidence of past environmental and climatic change, making Baikal important to earth-science research as well as regional geography.

Baikal is the world's largest freshwater lake by volume. The U.S. Geological Survey estimates that it holds about 23,000 cubic kilometres of water, roughly one-fifth of Earth's fresh surface water. More than 330 rivers and streams flow into the lake, including the Selenga, one of its major tributaries. Water leaves by a single surface outlet, the Angara River, which flows west from the lake and eventually joins the Yenisey system. These connections make the lake part of a much larger Siberian drainage network.

Baikal's age and relative isolation have helped produce an exceptionally distinctive freshwater fauna. UNESCO describes it as one of the world's richest and most unusual freshwater ecosystems, while research continues to document its endemic organisms. The Baikal seal is a freshwater-living pinniped found in the lake, and field research has shown that seals feed on endemic amphipods, including the planktonic species Macrohectopus branickii. Such relationships illustrate how the lake's deep-water environment and specialized species are connected.

UNESCO inscribed Lake Baikal on the World Heritage List in 1996 for its exceptional natural values. The lake is also affected by human infrastructure: a 2024 study archived by NOAA examined how the Irkutsk hydroelectric power plant on the Angara altered the lake's level fluctuations and outflow. This makes water management part of Baikal's contemporary geography, alongside its geology, biodiversity and role in regional science.